As far as I understand it is this way:
During D&SS you still have the possibility to buy a mayor or count title. These options will be removed once D&SS is ending. Buying a title at this point is granting you a guaranteed title as you get what you pay for and they are just selling as much titles as there are settlements/counties available.
In the reverse auction aka “Settlers of Elyria” all free regions will get a price tag that is slowly decreasing. The time of the auction is not set and the devs will be posting an announcement to let us know when the auction will start. In this auction you can move up the noble structure and even become a king but just if there is no one else already claiming the title. E.g. if you are a mayor in a county without a count you can buy the count title in the auction but all other mayors in the county have the same possibility and the same goes for the higher titles.
If the reverse auction is over all still free titles will be used by NPCs and you will not be able to buy a title this way anymore.
During exposition you can try to gain e.g. a county but all "title" progress will be reset on launch and gained titles will go back to the original owner regardless if it was a player or an NPC and just the development of the land will stay ingame. E.g. if you bought parcels you will have them at launch or if there was build a road this road will also be there at launch but you will not be be count of a county you claimed during exposition.
Once the game launch everyone can try to claim every title if they meet the ingame conditions. E.g. to get a mayor you might have to win an election or to become a king you need the support of the kingdoms dukes and have to defeat the old king.
